Composite pavement.



E. C. WALLACE.

COMPOSITEl PAVEMENT.

APPLICATION FILED Nov. z3, 1910.

U l Suva/Moz EDWIN` C. WALLACE, 0F EAST AUBURN, CALIFORNIA.

`COIlIIIPQSITE PAVEMENT.

Specication of Letters Patent.

Patented 9ct. W4', 1914.

Application filed November 23, 1910. Serial No. 593,860.

T0 all rwho-m it may concern Be it knownlthat I, EDWIN C. WALLACE, citizen of the United States, residing at East Auburn, in the county `of 'Placer and State of California., have invented new and useful Improvements in Composite Pavements, of which the following is la specification.

My present invention has relation to a wearing section of composite pavements; and it contemplates the provision of such a wearing section, adapted to be expeditiously laid at small cost of skilled] direction, ap-v paratus, labor. and material.

Way physicalA properties which it has hereto fore been impossible to attain in the wearing section of roadways or pavements.

It has long been recognized 1n the art, that other things being equal, the softer the bitu-A men used, and the richer in bituminous content, the greater thedurability of the mixture. The softness of the bitumen is determined by traic conditions. In order-to avoid displacement, knownas shifting, ridging, Waving, or shoving, it is customary on heavily .traveled streets to use bitumen of hard consistency (a #2 needle weighted to 100 grams to penetrate from ner. Instead of preparing the wearing section with a uniform mixture laid in a single coat as is usually done l prepare two dissimilar mixtures and lay in two coats using a hard bitumen for the primary coat by mixing it withA a mineral aggregate of relatively coarse particles and spreading this over thil foundations to a depth to give required thickness to the completed pavement. Prior to compression I spread over the top of this primary coat a superficial coat of fnemixture preparedl with a soft bituminous cenenting medium and relativelyine mineral aggregate making the' mixture richer in bitesA minous content than would be practical under p The wearing, section so constructed ,combines in a novel.

usual method of construction; the spreading of said superficial coat being to a depth of one fourth tofive eighths the thickness of the primary coat. After the two coats have been spread as described, compression is applied by means of a roller, tamper or other suitable device. However applied this is the first pressure to which either of the coats have been subjected, and the result is to force the fine soft and rich superficial coatl to blend with the harder, coarse and more rigid primary. coat at the tcp of the latter. So effective is the blending and bonding of the two coats that there is no cleavage like joint yor line ,of union between them,V but a single layer is-,produced with a rigid body to resist displacement and a softer more pliable top to resist abrasion.

In-the drawing, accompanying and hereby made a part hereof: vthe figure is avertical sectional view of a portion of a lwearing section of a composite pavement producedl in accordance with my invention.

.Thev invention alluded toV consists in' a process of producing a wearing section of a pavement, and for the sake of convenience and brevity. l will ldescribe in detail the fabrication of the pavement'from which description considered conjunctivel y with the lettered drawing it will be fu ly understood.

By reference to the drawing lit will appear that A is a prepared foundation which I would emphasize may be of any character consonant with thel purpose of my -invention.

' p B is the primary coat ofthe novel and advantageous wearing section, 4and C the superficial coat thereof.

` ln the preparation of theprimary coatl make use of a mineral aggregate of relatively coarsermaterial which may consist of crushed stone or gravel ora mixture/o -both combined when deemed expedient with a small proportion of sand or other,` fine mineral matter. This mineral aggregate is mixed with a relativelyvhard bituminous lcemeintirig medium,l (1n `which a #2 needle weighted to 100 grams will penetrate from 4 6 lmillimeters in 5 seconds at 77 degrees F.) in quantity sufficient to coat all the par.- ticles. The primary. coat will be spread loosely upon the previously prepared foundation to a depth of 2 inches. pression of the Vprimary coat herein described-a superficial coatr of relatively fine Prior to com ioe mineral matter composed of stone screenings or sand or a mixture of both, all of which will pass a screen of not less than 4 meshes per linear inch combined with a relatively soft bituminous cementing medium (a #2 needle vWeighted to 100 grams shall penetrate from 7g to 25 millimeters in 5 seconds at 77 degrees F.) in quantity suficient to coat all particles and form an agglutinated mass is spread loosely over the top of said primary coat, and compression is then applied as above set forth.

I claimv A pavement consisting of a: lower primary layer comprising loosely laid relatively large mineral bodies united by a relatively hard bituminous cement in a manner to afford relatively large lissures between the relatively large mineral bodies, which extend a substantial distance below the uppermost stratum of the primary layer, and an uppersecondary layer comprising a homogeneous mass formed of a relatively soft bituminous cement material mixed With iinely divided mineral bodies, the homogeneous mass being applied upon the upper surface of the primary layer, and having integral depending anchor arms thereof compressed into the fissures between the loosely laid relatively large mineral bodies of the primary layer, to extend a substantial distance below the uppermost stratum of the loyver layer whereby the homogeneous mass is securely anchored With and upon the primary layer to positively prevent creeping of the homogeneous mass.

In testimony whereof I have hereunto set my hand in presence of two subscribing Witnesses.'l

EDI/VIN C. WALLCE.

Witnesses:

A. L. HOUGH, VIRGINIA GARDNER. 

